Mediterranean spotted fever in child and adult patients: investigation from an endemic region in Bulgaria

Objectives: Mediterranean spotted fever (MSF) is a tick-borne endemic disease caused by Rickettsia conorii conorii and transmitted to humans by the brown dog tick Rhipicephalus sanguineus. It is characterized by fever, maculopapular rash and a tick bite skin lesion "tache noire". The disease affects all age groups and usually has mild to moderate course. It has long been considered a benign infection. However, very severe "malignant" forms with fatal outcome strongly influenced by the patients' age were also observed. We aimed to reveal the features of MSF in children by comparing them with some of the disease patterns in adults.

Methods: Our prospective study data are based on the monitoring of all inpatients of the Clinic of Infectious Diseases in Plovdiv City and environs, the largest MSF endemic region in Bulgaria. The total number of patients admitted and treated for MSF over a study period of 10 years is 549, the incidence reaching 9.44/100,000. MSF is confirmed by antibody response to a specific antigen measured by indirect immunofluorescence assay (IFA). IgG ≥ 128 and/or IgM > 64 were considered to be indicative of acute infection.

Results: Eighty-five (15.48%) patients were children up to 14 years of age and 464 (84.52%) were aged 15-85 years. The skin lesion "tache noire" was present in 73.68% of children, and in 76.93% of the older age groups; symptoms as anorexia, nausea, vomiting, abdominal pain, and diarrhoea were more frequent in children, till general weakness and malaise was prevalent in adults. Children accounted approximately for 70% of the disease mild forms. No lethality was registered in this age group. Even though there were isolated cases of severe and malignant forms, children did not undergo the fatal complications seen in adults.

Conclusion: Knowledge of the peculiarities of MSF in children will contribute to children's health protection, timely diagnose and disease prevention.

Keywords: Boutonneuse fever; Mediterranean spotted fever; Rickettsia conorii; children.